Lapping machine



June 21, 1938; w. F. EGGER LAPPING MACHINE Filed May 1 1956 4Sheets-Sheet l INVENTOR ATTORNEY6 4 Sheets-Sheet 2 ATTORNEYS.

W. F. EGGER LAPPING MACHINE Filed May 1, 1936 June 21, 1938.

June 21, 1938. v w. F. EGGER 2,121,025

LAPPING MACHINE Filed May 1, 1956 I INVENTOR. Q32, UaZzer .7 6996;

L9" .5. BY 5 5 Y M v 5 I7 TroRNEYs.

4 Sheets-Sheet 3 June 21, 1938. w;' F. EGGER 2,121,025

LAPPING MACHINE Filed May 1, 1956 4 Sheets-Sheet 4 .lllll;

ATTORNE -5 Patented June 21, 1938 PATENT OFFICE LAPPING MACHINE WalterF. Egger, Lakewood, Ohio, assignor to The AP. Schraner Company,Cleveland, Ohio,

a corporation of Ohio Application May .1, 1936, Serial No. 77,375

7 Claims.

This invention relates, as indicated, to improvements'in lappingmachines and relates in general to thetype of lapping, honing orpolishing machine such as is illustrated in myprior Patent No.'1,993,543,'dated March 5, 1935.

It is among the objects of the present invention to provide an improvedmeans for actuating from a single control station and by means of asingle control device the Variouselements of the apparatus so that theymay be actuated in the proper sequence requiredduring the operation ofthe machine.

A further and more'particular object of my invention is to provide animproved means for effecting an engagement between-the jaws which carrythe abrasive element and thearticle such as the crank shaft to be lapped-or polished, whereby such engagement'may be most efficiently effectedfrom a singlesource of power such-as a hydraulic jack.

As will be noted from anexamination'of the disclosures in my aboveidentifiedpatent, an apparatus-of the'charact'er to which the presentinvention relates usually comprises Work sup-- porting elements betweenwhich the crank shaft to be honed or lapped is rotatably supported withone of such elements commonly called the tail-stock relatively-movableto theother, whereby the securing of the work-article in the machine ismade possible.

The apparatus also includes a movable mounted head upon which issupported a plurality of work units, each unitadapted-to engage one ofthe crank pins of the crank shaft so that upon subsequent rotation ofthe crank shaft, the crank pin areas thereof will-be operated upon bysuch units. The apparatus also includes means for locking said units inpredetermined relation to the tilting or movable head, whereby-at theend of a particular lapping operation, all of such units may be lockedin predetermined relation to each other as well as to the head so thatwhen a new crank shaft is placed in the machineandthe head lowered'intooperative e ement, the various work units will occupy the properposition relatively to the crank pins of-the new crank shaft.

. Heretofore, these various steps of placing the machine in operationhave been performed manually and in proper sequence by an operator. Itis, as above indicated, one ofthe principal objects of my inventiontoprovide means for effecting all of the above named operations from asingle stationand furthermore, by means which although utilizing asingle source 'o'f'powe'r such as fluid under pressure, will perform thevarious operations in the predetermined desirable sequence.

With the advent of larger crank pin areas due particularly to increaseddiameters of the a time, be effective to impart the necessary workingpressure on the jaws which carry the abrasive elements and engage thecrank pins during the lapping or honing operation.

It is, as above indicated, another principal object of my invention toprovide an actuating device for the jaws which carry the abrasiveelements into engagement with the crank: pins whereby a single piston ofminimum diameter may beemployed'to first move the jaws at a relativelyrapid rate and with a small amount of force towards the work andthereupon at a consider-'- ably slower rate-but with a corresponding in?crease in the amount of force, move the jaws into working engagementwith the crank pins.

Other objects of my invention will appear as the description proceeds.

To the accomplishment of the. foregoing and related ends, saidinvention, then consists of the means hereinafter fully described andparticularly pointed out in the claims.

The annexed drawings and the following description set forth in detailcertain mechanism embodying the invention, such disclosed meansconstituting, however, but one of various mechanical forms in which theprinciple of the invention may be used.

In said annexed drawings:

Fig. 1 is a schematic diagram of an apparatus constructed in accordancewith the principles of my invention and showing in particular the pipesystem and connecting units or power jacks employed to accomplishthe'various movements of the apparatus which occur incidentally to theloading and unloading of the machine; Fig. 2 is a side elevational'viewin section of an apparatus constructed in accordance with my invent-ionand showing in particular the means. forbringing the jaws carrying theabrasive into and out of engagement with the crank shaft; Fig. 3'is anenlarged part sectional, part elevational View of a portion of theapparatus illustrated in Fig. 2; Fig. 4 is a transversesectional view ofa portion of the apparatus illustrated in Fig. 3 taken on a planesubstantially indicated by the line 4-4; "Fig.5 is a sectional view ofthe'control valve forming a part of the system illustrated in Fig. 1;Fig. 5a is a fragmentary sectional view, taken on the line 5a5a of Fig.2; Fig. 6 is a side elevational view, similar to Fig. 2, but stressing amodified form of the particular apparatus adapted to lock variousworking units relatively to each other; Fig. '7 is a part plan, partsectional view of a portion of the apparatus illustrated in Fig. 6,taken on a plane substantially indicated by the line 'i''I; and Fig. 8is a view showing the head actuating or tilting means.

Referring now more specifically to the drawings and more especially toFig. 1, the diagrammatic illustration here shown includes substantiallyall of the elements of the apparatus shown in my previously mentionedissued patent, the various working parts of the machine being shown onlydiagrammatically connected, however, by the control system which formspart of the present invention.

The head stock I and the tail stock 2 between which the work piece to beoperated upon is removably clamped and rotated, are showndiagrammatically and correspond generally, however, to the head and tailstocks 5 and 6, respectively, of Fig. 1 in my above identified patent.

Each of the work units adapted to engage and operate upon one of thecrank pins of the crank shaft is provided with an actuating piston orjack generally indicated by the numerals 3 and 4, the numeral 3 denotingthe jacks of work units which operate upon the connecting rod pins ofthe crank shaft and the ordinals 4 denoting the pistons or jacks of theunits which operate upon the main bearings of the crank shaft.

As the operating units carrying the pistons or jacks 3 and 4 are mountedon a movable head, the construction of which is more fully explained,and such head is actuated by means of a piston generally indicated at 5forming a part of the hydraulic jack unit 8, the means for locking thevarious work operating units relatively to each other, as well as to themovable head, which construction will be explained hereinafter ingreater detail, is energized by means of a piston I form-' ing a part ofthe hydraulic jack assembly 8. Other component parts of the circulatorysystem for the fluid which energizes the previously mentioned jacks andthus actuates the various parts of the machine, are a hydraulic pump 9,a 001- lecting sump or tank II], a control valve II, a pressureregulating valve I2, an overload relief valvev I3 and a shut-off valveI4. The pipe I5 leads from the sump ID to the pump 9; the pipe I3 fromthe pump 9 to the control valve II; the pipe II leads from the controlvalve II to the manifold I8 on one branch of the T I9 and through thepressure regulating valve I2 to return line 29 and manifold 2I.

The manifold I8 has supply lines 22 and 23 respectively leadingtherefrom to the tail stock 2 and the hydraulic jack 6 for actuating thehead of the machine. The manifold 2I has a conduit 24 leading to thelocking jack 8 and a plurality of conduits 25 respectively leading toone side of the jacks 3 and 4. A return manifold 28 is connected bymeans of a pipe 2'! to the jack 8 and a plurality of pipes 28 to thejacks 3 and 4. The return manifold 26 is connected through a T toanother return manifold 29 which is connected by means of pipes 39 and3I respectively to the tail stock 2 and the jack. 6 for actuating thehead.

The valve I3 is a simple overload relief valve, i. e., a closure member,not shown, is held onto the seat in the valve I3 by means of anadjustable spring so that when the pressure in the system exceeds apredetermined value, the fluid in the system will be vented back to thesump II].

The construction of the valve I2 is shown in detail in Fig. 5 and suchconstruction and its operation will now be described in detail.

It will be noted that the fluid supply to the valve I2 is throughconduit H which leads into the bore 32 in which is slidably mounted amovable valve member 33 normally under the influence of spring 34closing the passage between bores 32 and 35. The tension of the spring34 may be adjusted by means of the nut 36. Communicating with the bore.35 is a branch bore 31 in which is slidably mounted a plunger 38normally under the influence. of spring 39 sealing the passage betweenthe branch bore 35 and the relief bore 40, the relief bore being incommunication with the pipe 28. The tension of the spring 39 regulatingthe. pressure at which the relief bore 49 is opened is adjustablycontrolled by means of the nut 41.

It will be noted that the manifold 2| will not have fluid admittedthereto from the pipe I'I until after the pressure in the last-namedpipe is suflicient to elevate the plunger 33 against the spring 34. Theprimary function of the valve I2 is, therefore, to insure that the fluidin the manifold I8 is built up to a predetermined value and also afterthe fluid is admitted to the manifold 2|, to vent such fluid back to thesump in case the pressure on the same reaches a predetermined amount. Itwill, therefor, be seen that the pressure required to move the plunger33 upwardly and to provide communication between the bore 32 and thebranch bore 35 will be less than the pressure required to move theplunger 38 upwardly to provide communication between the branch bore 35and the relief bore 48. The fluid pressure at which the jacks 3, 4 and 8operate will, therefore, preferably be some value lying between thepressure which will move the plunger 33 upwardly and that pressure whichwill move the plunger 38 upwardly to open the passages respectivelycontrolled thereby. The provision of the valve I2 insures that therewill be no building into the jacks 3, 4 and 8 to cause a partialenergization of the same until the apparatus is in such condition thatthe devices respectively controlled by such jacks may be safelyoperated.

The function of the valve I4 is to close off the manifold 2'I which maybe desired on occasion if a crank shaft or similar work article is to beinserted in the machine and held there by the tail stock 2 but withoutengagement thereof by the abrasive holding jaws. When the valve I4 isclosed, then the relief valve I3 is relied upon to guard against damageto the apparatus in case of the building up in the machine of unexpectedpressures.

The work units presently to be described and which incidently form apart of the present invention are movably mounted and laterallysupported between arms 42 and 43, the outer ends of which are adapted tobe actuated to release or clamp the work units. For this purpose, thearm 42 has journalled in its outer end a nut I00, which is in threadedengagement with a nut I B I in the outer end of arm 43, the nut I00being restrained from axial movement with respect to arm 42 by meansof aset screw- I02, and the nut 1 81 being locked in adjusted position'bymeans of a locking detent I83 secured to the arm 43 by screw Hi4 andengaging teeth on a fiangeof nut IIH A rock shaft 44 extends through nutI88 and is keyed thereto; so that upon rotationof this shaft, the arms42 and 43 are relatively moved to clamp or release the work unit. Theshaft is rocked by means of a lever 45, to the rod 48 forming anextension'of the piston I. Energization of the jack 8 resulting in amovement of the piston 1' will, therefor.e, be translated into rotationof the shaft 44, and depending upon the direction of such rotation, thearms 43 will be moved either towards or away from arms 42. If the arms43 are moved towards the arms 42,.they will grip and hold the work unitssupported therebetween, thus locking the same relatively to each otheras well as the head by whichthey are supported.

A modification of this locking device has been found to be advantageousand particularly useful when the work units supported between the arms42 and 43 are stopped near the rear or inner ends of said arms. Thegripping action which takes place at thev outer ends of arms 42' and 43may be insufiicient to hold the units in place when they are stopped insuch position, particularly if a relatively heavy specimen is beinglapped, and to insure the holding in place of the units when they areso-stopped the modification most clearly-illustrated in Figs. 6 and '7has been constructed.

Toattain the desired result, nuts identical with those atthe outer endsof arms 42 and 43 are- .tion' of shaft 44 by the energization of thejack 8 will cause simultaneously a corresponding rotation of shaft 44amoving the inner ends of arms 43 toward or away from the arms 42 in thesame manner described above for the operation of the outer ends, thusgripping and holding in place the work units supported therebetweenregardless of the position in which they are stopped.

The construction of the work unit forming a part of this invention willnow be explained by having reference to Figs. 2 to 4.

As previously indicated, the machine to -which the present inventionrelates is generally similar to that illustrated in'm-y previouslymentioned prior patent. The workpiece suchas a crank shaft to be lappedis rotatably-supported between the head and tail stocks l and 2; Thework units which are employed to maintain successive sectionsof-a stripof abrasive material'49 inengagement with the crank pin 50 to be lappedor honed are likewise generally similar tothose illustrated in my priorpatent in that they comprise movably mounted arms 5| and 52 having jawsfashioned on their inner ends so as to snugly engage a circumferentialsection of the crank pin. The arms 5| and 52 are connected by means ofpins 53 and 54 to arms-55 and 56 in suchfashion that limited pivotalmovement between the two sets of arms is permitted. The arms 55 and 56are respectively pivotally secured to the head 5'! by means of pins 58and 59. The head 51, at its lower end, has a transverse extending borewithin which is mounted 'a compression spring .60 having contact buttonsBI and 62 which respectively engage the arms 55 and 56 to force apartthe lower ends of the same as well as the arms 5| and 52 respectivelycarriedthereby.

Extending upwardly through the head 51 is a piston rod 63 to the lowerend of which there is secured a cam plate 64. The cam plate 64 carriesguide rollers 65 which engage the opposite sides 66 of the opening inthe head 51 forthe purpose of guiding the cam plate 64 in its verticalreciprocation in such opening. The cam plate 64 is provided with twopairs of oppositely disposed faces t! and 68, the first pair beingarranged at a considerably greater angle to the longitudinal axis of therod 83 than the latter.

The arms 55 and 56 extend inwardly adjacent the cam plate '64 and carryrollers 89 which engage the cam faces 61 and 68.

Obviously, various specimens, such as crankshafts or camshafts, willvary in size, the circumference to be lapped of certain ones being lessthan that of others; consequently, if the same length of strip ofabrasive be used tolap those specimens of lesser circumference as isused to lap those of greater circumference, a certain amount of wasteresults. This waste has been reduced to a minimum in my present modifiedconstruction of the unit which operates tointermittently feed, a newlength of strip, by providing means whereby said length of strip may beI varied to accommodate the varied circumferences of particularspecimens. This unit comprises a ratchet 84 locatedat the end of arm 52,a oneway driving or ball clutch device 85 fixed to an arm 86 pivoted at81 toan arm 88 which is .pivoted at a stationary point 89 and a movablepoint '98.

The detailed operation of this unit is fully described in my aboveidentified prior patent and it is therefore believed necessary todescribe here only my improvement thereon which is as follows:

As the cam plate 64 is lowered, the roller 69, which engages the left.cam faces 87 and 68 is moved toward the right carrying with it thepivotal point 98 thus moving that portion of arm 88, below thestationary point 89,.toward the left, actuating arm 86 and clutch 85 inthe same direction to feed into place a new length of strip.

Obviously, the longer they stroke of arm 86, the

longer will be the new length of strip and to theaccomplishment of thisend additional pivotal points have been provided in the arm 88 such asat, 8111. and 8112' so that when the arm 86 is connected to one of thesepoints more remote from the pivotal point 88 such as 81a, said arm willbe moved through a greater distance due to its pivotal point moving inanarc of greater radius which results in a longer piece of abrasivebeing fed to-accommodate an increase in circumferenceof the specimen.

As most clearly illustrated in Fig. 2.. the upper end of the head '51has a cylinder 'lll mounted thereon in axial alignment with the rod thelower end of which cylinder is closed by means of a packing gland Hthrough which extends the upper end 12 of the piston rod 63. To theupper end of such piston rod there is secured a double acting piston.13. A stem generally indicated at M which is slidably supported in aknuckle has two passages Hi and H respectively formed therein, theformer providing communication between the pipe 25 and the space withinthe cylinder below the piston 73 and the passage 17'! providingcommunication between the pipe-'28 and-the space within the cylinderabove the piston 13. The

head 18 which is pivotally supported on the pin 19, as well as thevarious other details of construction of the apparatus included in thedrawings but which form no part of the presentinvention are believed tobe explained in sufficient detail in my above identified patent, that afurther description of their construction and mode of operation isbelieved unnecessary herein, it being noted, however, that the piston 5of the jack 6 is connected as by means of an adjustable connecting rod5a to the bar or link Si) by meansof Which movement of the head 18 aboutits supporting pin 19 is effected and controlled.

The operation of the above described construction with regard to thecontrol system shown in Fig. l, as well as the construction of theparticular work unit best illustrated in Fig. 3, is as follows:

A control handle 81 is provided and through which rod 82 is connected toarm 83 for the purpose of actuating the valve H.

Let it first be assumed that the machine is idle and it is desired toplace in the machine a work article such as a crank shaft to be lappedand to then bring the work units carrying the abrasive elements intoengagement with the crank pins of the shaft:The operator will firstactuate the lever B! in such a fashion as to cause a clockwise rotationof the plug in the valve H so that communication is afforded between theconduits l6 and H and 29 and 29a. Fluid under pressure from the pump 9will then flow through the valve H into the conduit I1 building up apressure therein against the pressure of spring 34 in the valve l2. Thevalve I2 will, therefore, cause a pressure to be built up in themanifold l8 from which the fluid will flow through conduits 22 and 23respectively to the tail stock 2 and the head actuating jack 6.

It is essential, of course, that the tail-stock engage the work piecebefore the head is moved into engagement therewith. Accordingly, theWork factor of the tail-stock jack will be less than the work factor ofthe head jack 6.

At this point I wish to explain what is meant by the term work factor asused in the ensuing description, as well as in the appended claims. Theterm work factor as used herein is the proportional relationship betweenthe area of the piston of a particular jack divided by the force of theapparatus tending to resist the movement of the jack. Thus,,for purposesof illustration, assume the cross sectional area of the tailstock pistonto be 4 and theforce required to move the tail-stock to be 2; thus thework factor of the tail-stock jack is 2.

Let is now be assumed that the area of the piston 5 of the head jack 6is 6 with the force tending to oppose movement of the piston 5 as 2;then the work factor of the head jack 6 will be As previously indicated,the effective cross sectional area of the piston of the tail-stock 2 isso proportioned relatively to the force required to be exerted therebythat the work factor of the tail-stock 2 Will be less than the workfactor of the head jack 6. Accordingly, even though fluid through acommon source of supply is introduced to both the tail-stock 2 and thehead jack 6, the tail-stock 2 will be first energized, thereby clampingthe work in the machine between the head and tail-stocks before the headjack 6 causes the head to move into operative position with respect tothe work piece.

As soon as the tail stock 2 and the head jack 6 have thus been actuatedin sequence, pressure will build up in the manifold I8 and I! to a valuesufficient to cause the plunger 33 to be moved upwardly against theaction of spring 34, thus admitting the fluid under pressure to themanifold 2|. Fluid under pressure from manifold 2| is, therefore,simultaneously admitted to the space below the piston 13 of the Workunit jacks TB and the space behind the piston l' of the work unitclamping jack 8. The work factor of the jacks 3 and 4 will preferably beless than the work factor of the jack 8 and accordingly, the piston 13will be forced upwardly causing an upward movement of the cam plate 64,which will result in an engagement of the arms 5! and 52 with the crankpin adjacent the particular work unit and as soon as such engagementtakes place, the jack 8 will cause a rotation of the shaft M in suchdirection as to free the Work units between the arms 42 and 43 placingthe machine in condition for operation.

The Work unit to be operated upon is thereupon rotated by means of thehead stock I and the lapping or honing operation continued for thedesired length of time.

The arrows which have been placed on the various conduits of the fluidcircuit shown in Fig. 1 indicate the direction of fluid flow during thecourse of the operation just described, 1. e., While the machine isbeing loaded and placed in condition to operate upon a work piece. Afterthe conclusion of the lapping or honing operations, the valve II will berestored to the position substantially indicated in Fig. 1 and the fluidflow through the system will then be reversed to the direction indicatedby the arrows 'restoring the various units to an inoperative position.

As previously indicated, one of the principal features of the presentinvention is the provision of a novel means whereby the arms 5| and 52may be brought into engagement with the work piece tobe operated upon.

When operating upon devices such as crank shafts, cam shafts and thelike, the distance between crank pins is usually very short and suchdistance determines, of course the diameter of the piston usable for thepurpose of closing the arms or jaws 5i and 52 onto the work. It is tothe solution of this particular problem that the apparatus most clearlyillustrated in Fig. 3 has been devised. The cam plate 64, it will benoted, on each side of its longitudinal axis has two angularly relatedfaces respectively extending at different angles to the line of movementof the plate. The face 61 is relatively steep sothat when the pistonmoves at a uniform rate, the arms 5|. and 52 will be brought towards theWork ata relatively rapid rate. This is possible for the reason thatlittle work is done in thus moving the arms towards the work; however,as soon as the arms approach the work rather closely, the roller 69 ofthe arm 55 rides over onto the face 68 of the am plate. Continuedmovement of the piston 13 at a uniformrate will, therefore, cause thearms and 52 to move into engagement with the work at a relatively slowerrate but with greater force. By this: novel connection between thepiston 13 and the arms 5|, I am able to utilize a relatively smallpiston as required by the distance between crank pins of the work andyet sufiiciently displace the arms 5| and 52 laterally of the work so asto sufiiciently clear the same and at the same time, exert sufficientpressure on the crank pin for the lapping or honing operation.

The relatively fiat inclination of the cam surface with respect to theaxis thereof results in a structure in which the lap is substantiallypositively held in a predetermined fixed relation with respect to thework surface so that as the lap encounters slight imperfectionsin suchsurface, it will have a greater tendency to cut away such imperfectionsas desired instead of yieldably riding over the same.

The function of the spring is, of course to maintain the roller 69 inengagement with the cam plate 64 so that the position of the arms 5| and52 will, at all times, be determined by the contour of the cam plate 64.

It should be noted at this point that instead of providing a cam platesuch as 64 with two angularly disposed straight faces such as 61 and 68,I may, for certain types of apparatus, prefer to make the operativefaces of the cam plate in a continuous curve with the upper portion ofthe face as viewed, for example, in Fig. 3, at a lesser angle to thelongitudinal axis of the rod 63 than the lower portions of the cam facewith which the rollers 69 contact, while the arms 5| and 52 are forcedinto engagement with the work.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the mechanismherein disclosed, provided the means stated by any of the followingclaims or the equivalent of such stated means be employed.

, I therefore particularly point out and distinctly claim as myinvention:-

1. In apparatus of the character described, the combination of aplurality of lapping units, a movably supported head carrying saidlapping units, locking means for securing said lapping units relativelyto said head, a movable work en gaging member, a plurality of fluidactuated operating devices respectively connected to said work engagingmember, said head, said lapping units and said locking means, and asingle control valve for simultaneously connecting all of said operatingdevices to a single source of fluid under pressure, the work factor ofsaid operating devices being so proportioned as to be effective inproper sequence.

2. In apparatus of the character described, the combination of aplurality of lapping units, a movably supported head carrying saidlapping units, locking means for securing said lapping units relativelyto said head, a movable work engaging member, a plurality of fluidactuated jacks respectively connected to said work engaging member, saidhead, said lapping units and said locking means, and a single controlvalve for simultaneously connecting all of said jacks to a single sourceof fluid under pressure, the fluid volume capacity of the several jacksbeing so proportioned that the same operate the devices connectedthereto in predetermined sequence.

3. In apparatus of the character described, the combination of aplurality of lapping units, a movably supported head carrying saidlapping units, locking means for securing said lapping units relativelyto said head, a movable work engaging member, a plurality of hydraulicjacks respectively connected to said work engaging member, said head,said lapping units and said locking means, and a single control valvefor simultaneously connecting all of said jacks to a single source ofliquid under pressure, the hydraulic volume capacity of said jacks beingso proportioned that the same operate the devices connected thereto inpredetermined sequence.

4. In apparatus of the character described, the combination of aplurality of relatively movable work engaging jaws, actuating armsconnected to said jaws, a movable cam member adapted to engage said armsto actuate said jaws, said cam member so formed that upon movementthereof at a uniform rate said jaws will be moved toward the work at arelatively rapid rate and into engagement therewith at a slower rate.

5. In apparatus of the character described, the combination of aplurality of relatively movable work engaging jaws, actuating armsconnected to said jaws, a movable cam member adapted to engage said armto actuate said jaws, said cam provided with angularly related workfaces where by upon movement thereof at a uniform rate said jaws will bemoved toward the work at a relatively rapid rate and into engagementtherewith at a slower rate.

6. In apparatus of the character described, the combination of aplurality of relatively movable work engaging jaws, actuating armsconnected to said jaws, a movable cam member adapted to engage said armsto actuate said jaws, said cam member so formed that upon movementthereof at a uniform rate said jaws will be moved toward the work at arelatively rapid rate and into engagement therewith at a slower rate andmeans for moving said cam member.

7. In apparatus of the character described, the combination of aplurality of relatively movable work engaging jaws, actuating armsconnected to said jaws, a movable cam member adapted to engage said armsto actuate said jaws, said cam provided with angularly related workfaces whereby upon movement thereof at a uniform rate said jaws will bemoved toward the work at a relatively rapid rate and into engagementtherewith at a slower rate and a fluid actuated piston for moving saidcam member.

WALTER F. EGGER.

